program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  n, i, b : integer;
begin
  readln (n);
  b:=0;
  if (n mod 2 = 0) then
    for i:= 1 to (n div 2) do
      b:=b+(i*2);
  if (n mod 2 <> 0) then
  begin
    b:=3;
    for i:=2 to (n div 2) do
      b:=b+(i*2+1);
  end;
  writeln (b);
  readln;
end.
 